Developing the ultrafine-grained epsilon mircrostructure via dynamic phase transformation at elevated temperatures

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K21567
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Material processing/Microstructural control engineering; Biomedical engineering/Biomaterial science and engineering
• Research Institution: Sendai National College of Technology
• Principal Investigator: MORI Manami 仙台高等専門学校, 総合工学科, 助教 (80731512)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 生体用金属材料 / ナノε組織 / 熱間加工

Outline of Final Research Achievements

Due to the excellent wear and corrosion resistances, biomedical Co－Cr－Mo alloys have been used in various orthopedic devices. In this study, we focused on the hexagonal close-packed ε phase, which is an equilibrium phase at lower temperatures, and tried to fabricate its ultrafine-grained (UFG) microstructures. We found for the first time that the UFG microstructures of the ε phase can be produced via dynamic phase transformation from the metastable γ (fcc) matrix by hot deformation performed at temperatures where the ε phase is stable.

Free Research Field

材料加工・組織制御工学

Academic Significance and Societal Importance of the Research Achievements

整形外科用ロッド等に使用される生体用Co－Cr－Mo合金は、長寿命化の観点から更なる高強度化が重要な課題である。そこで、耐摩耗性に優れるが研究例が少ないε相に着目し、結晶粒超微細化を組み合わせることにより、本合金の更なる強度化や新規な高強度化手法の確立することができた。また、超微細ε組織の形成は加工誘起マルテンサイト変態と関連していることが示唆され、新しい動的変態メカニズムの可能性を見出し、学術的に重要な知見を得ることができた。